Separation of olefins from cracked naphtha



Oct- 12. 1954 P. L. GcMoRY SEPARATION OF OLEFINS FROM CRACKED NAPHTHA Filed Dec. 28, 1951 mm Qu?. mmS )1.--- Jl 20mm/Somer E f omNINom ATTORNEY Patented Oct. 12, 1954 SEPARATION OF -OLEFINS FROM CRACKED NAPHTHA Paul L. Gomery, Bethesda, Md., assigner to Phillips Petroleumv Company, Aa corporation of Dela- Wavre Application December 28, 1951,` Serial No. 263,836

1 claim. l

This invention relates to a method for producing alkyl-aromatic sulfonates suitable for .use as detergents. In one aspect, it relates to an improved method for preparing feed stocks for an olefin-aromatic condensation reaction step in detergent manufacture employing a prior sulfating step in a manner and under conditions set forth hereinbelow. In another aspect, it relates'to an improved method for separating the'long-chain olens from undesired short-chain alkyl aromatics contained in a cracked naphtha employing a hydrolysis step to separate sulfated olens contained in said cracked naphtha therefrom in a manner and under conditions set forth hereinbelow. In still another aspect, the invention relates to a method for the preparation of an olefin-free cracked naphtha.

One method for producing synthetic detergents is accomplished by condensing the long-chain olefins contained in a cracking naphtha with benzene, toluene, or xylene and then sulfonating the resulting alkyl benzene. The initial boiling point of the cracked naphtha can be selected sufiiciently high so that olefins lower than Cv are eliminated. The boiling range of the naphtha is usually selected so that olefins .in the range C7 to Cm are included. Thus, the boiling range of the cracked naphtha is usually A200 to 500 F. Such a cracked naphtha usually contains shortchain alkyl aromatics which are not-desirable because they also condense with 'the long-chain olefins and form sulfonated products, in the -sulfonation step, which are inferior detergents. A major problem in the preparation of" synthetic vdetergents from the long-chain olefins contained in a cracked naphtha is the removal of these short-chain alkyl aromatics from the cracked naphtha. Various methods for removing these undesirable alkyl aromatics have beenk proposed with varying degrees of success.

An object of this invention ris toprovidewan improved method for producing detergents.

Another object is to provide an olefin-free cracked naphtha.

Another object is to provide an improved method for the separation of olens and aromatics Whose boiling points are similar.

Another object -is toiprovide a method for sulfating olefins While in the presence of alkyl aromatics.

Another object is to provide a method `for removing olens from crack-ed naphtha.

It has occurred to me that the sulfonation .reaction which usually follows the condensation of the `olein and aromatic might be employed substantially purefstate.

before the condensation stepv to provide a method for separating the long-chain olefins from the short-chain alkyl aromatics. Pursuing this conception, I have discovered a novel combination of steps which provides an improved method for removing olefins from a cracked naphtha in substantially pure form by sulfation of the olefins whereby the olens are removed in the aqueous acid phase. Upon hydrolysis, the alkyl-sulfates thus formed are converted into water-insoluble alcohols'andare used as such in the condensationrand sulfonation steps which follow to produce an improved detergent. If desired, the alcohols canL be converted back to the original'olenns by known methods, such as dehydration over bauxite.

Thus, according to the process of this invention a cracked naphtha boiling in the range 200 to 500 F. is subjectedto mild sulfation by sulfuric acid of 65 to 85 weight percent concentration at a temperature sufciently low to prevent polymerization, whereby the olens are substantially sulfatedand the short-chain alkyl aromatics are substantially unreacted. The aqueous acid phase from the sul'fa-tion reaction is then hydrolyzed by aqueous dilution followed by heating whereby vthe alkyl sulfates are converted into substantially Water-insoluble alcohols and are recovered ina The short-chainl alkyl aromatics areretained in the hydrocarbon phase.

The cracked naphtha, freed of. olens contain- .ing the unreacted alkyl aromatics, is a useful product of the process.

The mild ,sulfation of the cracked naphtha to convert theolefins into alkyl sulfates can be accomplished inone stepemploying a concentration in the above referred to range of concentrations of sulfuric acid. My preferred method is to employ a two-step sulfation reaction wherein the-acid used inthe first step contains 65 toy '75 Weight per cent HzSOl and the acid used in the second step contains 75 to' 85 weight per cent H2SO4, the other reaction conditions being substantially the same in both steps.

The temperatures employed in this process are, at Aleast'partly, dependent upon other operating variables such as acid concentration, contact time and vole'ln content of the feed. The proper temperature for a given set of conditions can be determined by mere routine test. Control of ternperatur-e rise is probably more important thany is the absolute temperature. When a one step process is employed temperatures yare preferably vin the range 20 to 40 F., more preferably in the range '25 to 35` F.

When a two-step process is employed the temperatures of the two steps can be the same or different within the above limits. I have found that the more easily sulfated olens are removed first so that a separation of more easily sulfated oleiins from more diiiicultly sulfated olens is possible inthe process of this invention. Thus a weaker acid and lower temperatures are advantageously employed in the rst step and stronger acid and higher temperatures are employed in the succeeding steps.

The sulfation reaction performed upon the cracked naphtha in the process of my invention can be accomplished with more dilute sulfuric acid than is required for the sulfonation of the condensation product of benzene with long-chain olens and thus the used acid from the sulfonation step can be used to sulfate the olens contained in the cracked naphtha. agents can also be used for this reaction, however, more care is required in maintaining low temperatures and short .reaction time which are necessary when a more vigorous sulfating and/or sulfonating agent is used. The following example provides a demonstration of the operation of the invention.

Example I A cracked naphtha obtained by the catalytic cracking of a gas oil from a West Texas crude is fractionated to produce a cut boiling in the range 200 to 500 F. Such a cracked naphtha usually contains approximately per cent oleiins.' The naphtha is countercurrently contacted in a first reactor, with sulfuric acid of 65 per cent concentration, with agitation at a temperature maintained in the range 25 to 30 F. and at'substantially atmospheric pressure. The feed rate of acid and naphtha is maintained so that a contact time of approximately one hour results between the acid and hydrocarbon.

The effluent from this reactor is passed to a settling Zone. The aqueous acid phase is removed from the bottom of the settler, diluted to 25 to 35 weight per cent concentration of H2SO4 with water and heated to a temperature in the range 100 to 200 F. so as to hydrolyze the alkyl sulfates present in the acid to alcohols. These water-insoluble alcohols are then removed from' the hydrolyzing Zone and passed to the alcoholaromatic condensation. The dilute acid removed from the hydrolyzing Zone is passed to an acid concentrator.

The hydrocarbon phase from the reactor effluent settling zone is then countercurrently contacted in a second reactor with sulfuric acid of 85 per cent concentration, with agitation at a temperature maintained in a range 35 to 40 F. and at substantially atmospheric pressure. The contact time in this second reactor is also maintained at approximately one hour. The eiiluent from this second reactor is passed to a second settling zone from which the aqueous acid phase is withdrawn, diluted with water to a H2504 concentration of from 25 to 35 weight per cent and heated to a temperature in the range 100 to 200 F. to hydrolyze the alkyl sulfates to alcohols. The alcohols are withdrawn from this second hydrolyzing zone and combined with the alcohols from the first hydrolyzing zone and passed to the alcohol-aromatic condensation and sulfonation steps. The dilute acid from the second hydrolyzer zone is combined With dilute acid from the first hydrolyzer zone and passed toan acid concentrator. The hydrocarbons from the second reactor eluent settler are then passed to storage.

Advantages of the present invention Will be apparent from a description of the accompanying drawing which is a schematic illustration of one embodiment of this invention. The cracked naphtha feed stock is cooled in cooler I I and introduced into the lower zone of reactor I2. Sulfuric acid is cooled in cooler I3 and introduced into the upper part of reactor I2. Contents of reactor I2 are maintained in a state of agitation y by stirrer I4. The effluent of reactor I2 is With- Other sulfating drawn through line I5 to settler I 6. The acid phase of the reactor eiiluent is Withdrawn from settler I6 through line I1 where it is diluted with Water introduced through line I8. It is heated in heater I9 and passed to hydrolyzing zone 2|. Dilute acid is withdrawn from hydrolyzing zone 2| through line 22 and passed to an acid concentrator (not shown). Alcohols formed in the process are removed from -hydrolyzing zone 2| through line 23 and passed to alcohol-aromatic condensation step (not shown). Hydrocarbons from settler I6 are cooled in cooler 24, passed to the lower zone of reactor 25 and sulfuric acid passed through cooler 26 to the upper zone of reactor 25. The contents of reactor I2 are maintained in a state of agitation by stirrer 21. The etliuent from reactor 21 is passed via line 28 to settler 29 from which the acid phase is removed via line 3|, diluted with water from line 32, heated in heater 33 and passed to hydrolyzing zone 34. Alcohols formed in this step are withdrawn from hydrolyzer zone 34 via line 35, combined with the alcohols in line 23 and passed to alcohol-aromatic condensation step (not shown). Dilute acid is drawn from hydrolyzer 34 and passed.through line 36, combined with dilute acid, withdrawn from hydrolyzer 2l and the combined stream is passed to an acid con- -centrator (not shown) Hydrocarbons comprising parailins, naphthenes and short-chain alkyl aromatics are removed from settler 29 and passed via line 31 to storage.

As stated, my preferred method of operation comprises two steps wherein in the first step a more dilute sulfating acid is used in order to sulfate and remove the more readily sulfated olens. A more concentrated sulfating acid is then used to sulfate the remaining oleiins. While it is possible to conduct this process employing only the more concentrated sulfuric acid in one step, I have found that in some cases polymerization of the more reactive oleins results. In some cases it may be preferred to recover a smaller overall percentage of oleiins in order to remove the oleiins from a greater quantity of cracked naphtha.

Variation and modification are possible within the scope of this disclosure of this invention, the essence of which is that undesirable short-chain alkyl aromatics can be separated from the oleiins in a hydrocarbon mixture comprising parafns, short-chain alkyl aromatics, naphthenes and long-chain olefins by sulfating the longchain olefms with sulfuric acid and removing them in the resulting aqueous acid phase and subsequently hydrolyzing these alkyl sulfates into water-insoluble alcohols.

I claim:

A method for producing an improved feed stock for a process for producing long-chain a1- kyl aromatic sulfonates from the olens contained in a cracked naphtha comprising longchain olens, the corresponding alcohols of which are water insoluble, short-chain alkyl aromatics and paraiiins which comprises contacting, in a first reactor, said cracked naphtha with sulfuric acid of 65 to '75- per cent concentration at a temperature in the range 20 to 40 F. for 30l minutes to two hours; withdrawing a resulting aqueous acid phase; diluting said acid phase to 25 to 35 per cent concentration so as to hydrolyze alkyl sulfates produced in said reactor; separating and recovering resulting substantial- 1y water-insoluble alcohols; withdrawing unreacted hydrocarbons from said first reactor; contacting said hydrocarbons, in a second reactor, with sulfuric acid of 75 to 85 per cent concentration at a temperature in the range 20 to 40 F. for 30 minutes to two hours; withdrawing a resulting aqueous acid phase, diluting said acid phase to 25 to 35 per cent concentration so as to hydrolyze alkyl sulfates produced in said second reactor; separating and recovering substantially water-insoluble alcohols; withdrawing from said second reactor a substantially olenfree hydrocarbon mixture as a product of the process; combining said alcohols from said rst hydrolyzing step and said second hydrolyzing step so as to provide said improved feed stock.

References Cited in the iile of this patent UNITED STATES PATENTS Number Name Date 1,483,835 Ramage Feb. 12, 1924 1,486,647 Ellis et al. Mar. 11, 1924 2,326,505 Tulleners Aug. 10, 1943 2,390,835 Hennion et al Dec. 11, 1945 2,596,091 De Benneville May 13, 1952 2,597,834 Claussen May 20, 1952 

